Hi
I was wondering how to find molar absorptivity of inorganic nanoparticle in the mid IR range? If I would like to apply the Beer-Lambert law then particles should be dissolved in a solvent and use the formula i.e A=epsilon*c*l. But unfortunately most of the solvents have mid IR absorption which will interfere with the particles mid IR absorption. In order to avoid that what should you recoomend. If I do in ATR mode would it be possible to get the data of molar absorptivity? Kindly share your experience.
There are plenty of sites that will show the RI (real and imaginary) against wavelength for gold. Fir example: http://refractiveindex.info/?shelf=main&book=Au&page=Rakic
Mie theory allows you to calculate the wavelength dependent absorption for nanoparticles (often a peak around 500 nm making typical gold sols purplish in color). See:
July 30th, 2013 Optical properties of gold
https://www.brainshark.com/malvern/vu?pi=883587233&text=M021507
and February 25th, 2014 The life of Gustav Mie and the development of the Lorenz-Mie solution to Maxwell’s equations http://tinyurl.com/mt97tp3
Dr. Rawle
Thanks for the link. I was wondering for MoS2 which is not reported in literature as far as my search is concerned. But I am not sure though whether people have really done it. Thats why posed a general question how to measure absorptivity for any material. Anyway I will look into your links.
Hi Ankur Doesn't this link answer your question?
http://refractiveindex.info/?shelf=main&book=MoS2&page=Beal
Hi Dr. Rawle
Many thanks for the link. I got it also. But I am interested in 7 to 10 micron. Here it is reported up to 1.5 micron. I am not sure whether it is good to extrapolate the data up to 10 micron since after 1 micron it looks very flat. But my gut feeling says it is not good to extrapolate since it might have more extinction in the mid IR level. If you can help me this regard that would be awesome. I guess I am clear to you. Many thanks for your interest.
regards
Ankur
Hi Ankur I agree with you and I don't think it's wise to extrapolate - an absorption band may just suddenly occur. I can't seem to find anything of relevance either. Perhaps you'd have to carry out a direct ellipsometry or reflectivity measurement in the region of interest?
The problem is what ellipsometer we have that does not have the source in the mid IR range. Do you think if I do FTIR of the sample can we estimate alpha (absorptivity) from that. And then calculate n and k fom molar absorptivity? I am not quite sure is there any relevant formula to calculate n and k from alpha.
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanostructured Materials
- Nanoparticles